<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .b1{
        width: 100%;
        height: 1500px;
        background: red;
    }
    .b2{
        width: 100px;
        height: 100px;
        position: fixed;
        right: 0;
        bottom: 200px;
        background-color: yellow;
    }
</style>
<body>
    <div class="b1"></div>
    <div class="b2"></div>
</body>
</html>